Metal matric composites may be produced by dispersing a second phase powder into a molten metal during casting. Dispersing a powder into a molten metal, however, may be difficult. For example, powder tends to float or to sink and cluster, which may result in uneven distribution. Powder clusters may be difficult to break up, even with vigorous stirring action. The problem may be accentuated in the case of large ingots such as direct-chill ingots cast for aluminum rolling mill process.